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• Algorithm for finding the best routes for food distribution in game

  - by Tautrimas

  Hello, I'm designing a city building game and got into a problem. Imagine Sierra's Caesar III game mechanics: you have many city districts with one market each. There are several granaries over the distance connected with a directed weighted graph. The difference: people (here cars) are units that form traffic jams (here goes the graph weights). Note: in Ceasar game series, people harvested food and stockpiled it in several big granaries, whereas many markets (small shops) took food from the granaries and delivered it to the citizens. The task: tell each district where they should be getting their food from while taking least time and minimizing congestions on the city's roads. Map example Sample diagram Suppose that yellow districts need 7, 7 and 4 apples accordingly. Bluish granaries have 7 and 11 apples accordingly. Suppose edges weights to be proportional to their length. Then, the solution should be something like the gray numbers indicated on the edges. Eg, first district gets 4 apples from the 1st and 3 apples from the 2nd granary, while the last district gets 4 apples from only the 2nd granary. Here, vertical roads are first occupied to the max, and then the remaining workers are sent to the diagonal paths. Question What practical and very fast algorithm should I use? I was looking at some papers (Congestion Games: Optimization in Competition etc.) describing congestion games, but could not get the big picture. Any help is very appreciated! P. S. I can post very little links and no images because of new user restriction.

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• How to count term frequency for set of documents?

  - by ManBugra

  i have a Lucene-Index with following documents: doc1 := { caldari, jita, shield, planet } doc2 := { gallente, dodixie, armor, planet } doc3 := { amarr, laser, armor, planet } doc4 := { minmatar, rens, space } doc5 := { jove, space, secret, planet } so these 5 documents use 14 different terms: [ caldari, jita, shield, planet, gallente, dodixie, armor, amarr, laser, minmatar, rens, jove, space, secret ] the frequency of each term: [ 1, 1, 1, 4, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1 ] for easy reading: [ caldari:1, jita:1, shield:1, planet:4, gallente:1, dodixie:1, armor:2, amarr:1, laser:1, minmatar:1, rens:1, jove:1, space:2, secret:1 ] What i do want to know now is, how to obtain the term frequency vector for a set of documents? for example: Set<Documents> docs := [ doc2, doc3 ] termFrequencies = magicFunction(docs); System.out.pring( termFrequencies ); would result in the ouput: [ caldari:0, jita:0, shield:0, planet:2, gallente:1, dodixie:1, armor:2, amarr:1, laser:1, minmatar:0, rens:0, jove:0, space:0, secret:0 ] remove all zeros: [ planet:2, gallente:1, dodixie:1, armor:2, amarr:1, laser:1 ] Notice, that the result vetor contains only the term frequencies of the set of documents. NOT the overall frequencies of the whole index! The term 'planet' is present 4 times in the whole index but the source set of documents only contains it 2 times. A naive implementation would be to just iterate over all documents in the docs set, create a map and count each term. But i need a solution that would also work with a document set size of 100.000 or 500.000. Is there a feature in Lucene i can use to obtain this term vector? If there is no such feature, how would a data structure look like someone can create at index time to obtain such a term vector easily and fast? I'm not that Lucene expert so i'am sorry if the solution is obvious or trivial.

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• nhibernate - mapping with contraints

  - by Tobias Müller

  Hello everybody, I am having a Problem with my nhibernate-mapping and I can't find a solution by searching on stackoverflow/google/documentation. The database I am using has (amongst others) two tables. One is unit with the following fields: id enduring_id starts ends damage_enduring_id [...] The other one is damage, which has the following fields: id enduring_id starts ends [...] The units are assigned to a damage and one damage can have zero, one or more units working on it. Every time a unit moves to annother damage, the dataset is copied. The field "ends" of the old record and "starts" of the new record are set to the current time stamp, enduring_id stays the same. So if I want to know which units were working on a damage at a certain time, I do the following select: select * from unit join damage on damage.enduring_id = unit.damage_enduring_id where unit.starts <= 'time' and unit.ends = 'time' (This is not an actualy query from the database, I made it up to make clear what I mean. The the real database is a little more complex) Now I want to map it that way, so I can load all the damages which are valid at one time (starts <= wanted time <= ends) and that each of them has a Bag with all the attached units at that time (again starts <= wanted time <= ends). Is this possible within the mapping? Sorry if this is a stupid question, but I am pretty new to nhibernate and I have no clue how to do it. Thanks a lot for reading my post! Bye, Tobias

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• How can I extend this SQL query to find the k nearest neighbors?

  - by Smigs

  I have a database full of two-dimensional data - points on a map. Each record has a field of the geometry type. What I need to be able to do is pass a point to a stored procedure which returns the k nearest points (k would also be passed to the sproc, but that's easy). I've found a query at http://blogs.msdn.com/isaac/archive/2008/10/23/nearest-neighbors.aspx which gets the single nearest neighbour, but I can't figure how to extend it to find the k nearest neighbours. This is the current query - T is the table, g is the geometry field, @x is the point to search around, Numbers is a table with integers 1 to n: DECLARE @start FLOAT = 1000; WITH NearestPoints AS ( SELECT TOP(1) WITH TIES *, T.g.STDistance(@x) AS dist FROM Numbers JOIN T WITH(INDEX(spatial_index)) ON T.g.STDistance(@x) < @start*POWER(2,Numbers.n) ORDER BY n ) SELECT TOP(1) * FROM NearestPoints ORDER BY n, dist The inner query selects the nearest non-empty region and the outer query then selects the top result from that region; the outer query can easily be changed to (e.g.) SELECT TOP(20), but if the nearest region only contains one result, you're stuck with that. I figure I probably need to recursively search for the first region containing k records, but without using a table variable (which would cause maintenance problems as you have to create the table structure and it's liable to change - there're lots of fields), I can't see how.

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• How to allow anonymous login in org.apache.ftpserver?

  - by ablmf

  I wrote a little code like this to start an ftp server embedded in my application. It's based on apache ftpserver I found that anonymous user could not login. Client keeps get 530. Do I have add a configure file for ftp? I can not find any API to create a User to add to UserManger. private void start_ftp() throws FtpException { FtpServerFactory serverFactory = new FtpServerFactory(); ListenerFactory factory = new ListenerFactory(); // set the port of the listener factory.setPort(DEF_FTP_PORT); // replace the default listener serverFactory.addListener("default", factory.createListener()); Ftplet fl = new MyFtplet(); Map<String, Ftplet> map_ftplest = new LinkedHashMap<String, Ftplet>(); map_ftplest.put("default", fl); serverFactory.setFtplets(map_ftplest); UserManagerFactory u_factory = new PropertiesUserManagerFactory(); UserManager u_manager = u_factory.createUserManager(); //u_manager. Boolean b = u_manager.doesExist("anonymous"); serverFactory.setUserManager(u_manager); // start the server server = serverFactory.createServer(); server.start(); }

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• Spring Stripes framework problem

  - by ali

  I am new to stripes and am attempting to integrate spring into stripes In the following code : public class ContactFormActionBeanTest { private static MockServletContext mockServletContext; private static MockHttpSession mockSession; @BeforeClass public static void setup() throws Exception { mockServletContext = new MockServletContext("webmail"); Map<String,String> params = new HashMap<String,String>(); params.put("ActionResolver.Packages", "stripesbook.action"); params.put("Extension.Packages", "stripesbook.ext," + "net.sourceforge.stripes.integration.spring"); mockServletContext.addFilter(StripesFilter.class, "StripesFilter", params); mockServletContext.setServlet(DispatcherServlet.class, "DispatcherServlet", null); mockSession = new MockHttpSession(mockServletContext); mockServletContext.addInitParameter("contextConfigLocation", "/WEB-INF/applicationContext-test.xml"); ContextLoaderListener springContextLoader = new ContextLoaderListener(); springContextLoader.contextInitialized( new ServletContextEvent(mockServletContext)); // Load mock user MockRoundtrip trip = new MockRoundtrip(mockServletContext, MockDataLoaderActionBean.class, mockSession); trip.execute(); // Login mock user trip = new MockRoundtrip(mockServletContext, LoginActionBean.class, mockSession); trip.setParameter("username", "freddy"); trip.setParameter("password", "nadia"); trip.execute("login"); } I get null in springContextLoader ContextLoaderListener springContextLoader = new ContextLoaderListener(); and test fails. Am I missing something? I am using eclipse with maven. Also when I try to deploy it for tomcat 6.0 I get following warnings: WARN net.sourceforge.stripes.util.ResolverUtil - Could not examine class 'stripesbook/ext/ContactFormatter.class' due to a java.lang.UnsupportedClassVersionError with message: Bad version number in .class file (unable to load class stripesbook.ext.ContactFormatter) I have checked to be sure that I am compiling with Java 5(set JDK compiler to 1.5) instead of 1.6 (Java 6); but didn't work out for me and still have problems running spring-stripes integrated project.

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• What's the best way to read a UDT from a database with Java?

  - by Lukas Eder

  I thought I knew everything about UDTs and JDBC until someone on SO pointed out some details of the Javadoc of java.sql.SQLInput and java.sql.SQLData JavaDoc to me. The essence of that hint was (from SQLInput): An input stream that contains a stream of values representing an instance of an SQL structured type or an SQL distinct type. This interface, used only for custom mapping, is used by the driver behind the scenes, and a programmer never directly invokes SQLInput methods. This is quite the opposite of what I am used to do (which is also used and stable in productive systems, when used with the Oracle JDBC driver): Implement SQLData and provide this implementation in a custom mapping to ResultSet.getObject(int index, Map mapping) The JDBC driver will then call-back on my custom type using the SQLData.readSQL(SQLInput stream, String typeName) method. I implement this method and read each field from the SQLInput stream. In the end, getObject() will return a correctly initialised instance of my SQLData implementation holding all data from the UDT. To me, this seems like the perfect way to implement such a custom mapping. Good reasons for going this way: I can use the standard API, instead of using vendor-specific classes such as oracle.sql.STRUCT, etc. I can generate source code from my UDTs, with appropriate getters/setters and other properties My questions: What do you think about my approach, implementing SQLData? Is it viable, even if the Javadoc states otherwise? What other ways of reading UDT's in Java do you know of? E.g. what does Spring do? what does Hibernate do? What does JPA do? What do you do? Addendum: UDT support and integration with stored procedures is one of the major features of jOOQ. jOOQ aims at hiding the more complex "JDBC facts" from client code, without hiding the underlying database architecture. If you have similar questions like the above, jOOQ might provide an answer to you.

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• Access generic type parameter at runtime?

  - by Bart van Heukelom

  Event dispatcher interface public interface EventDispatcher { <T> EventListener<T> addEventListener(EventListener<T> l); <T> void removeEventListener(EventListener<T> l); } Implementation public class DefaultEventDispatcher implements EventDispatcher { @SuppressWarnings("unchecked") private Map<Class, Set<EventListener>> listeners = new HashMap<Class, Set<EventListener>>(); public void addSupportedEvent(Class eventType) { listeners.put(eventType, new HashSet<EventListener>()); } @Override public <T> EventListener<T> addEventListener(EventListener<T> l) { Set<EventListener> lsts = listeners.get(T); // ****** error: cannot resolve T if (lsts == null) throw new RuntimeException("Unsupported event type"); if (!lsts.add(l)) throw new RuntimeException("Listener already added"); return l; } @Override public <T> void removeEventListener(EventListener<T> l) { Set<EventListener> lsts = listeners.get(T); // ************* same error if (lsts == null) throw new RuntimeException("Unsupported event type"); if (!lsts.remove(l)) throw new RuntimeException("Listener is not here"); } } Usage EventListener<ShapeAddEvent> l = addEventListener(new EventListener<ShapeAddEvent>() { @Override public void onEvent(ShapeAddEvent event) { // TODO Auto-generated method stub } }); removeEventListener(l); I've marked two errors with a comment above (in the implementation). Is there any way to get runtime access to this information?

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• Liferay hook: filter url giving filterstart error and current url generates exception null

  - by jack

  I'm trying to make an autologinfilter in Eclipse using a liferay hook. Now I've added the: <filter> <filter-name>myautologinfilter</filter-name> <filter-class>bla.bla.xyz</filter-class> </filter> <filter-mapping> <filter-name>myautologinfilter</filter-name> <url-pattern>/c/login/myurl</url-pattern> </filter-mapping> To the liferay hook's web.xml. In the liferay-hook.xml I added: portal.properties And in that hook.xml I added: auto.login.hooks=bla.bla.xyz bla.bla.xyz implements AutoLogin, but for now it's pretty gutted: @Override public String[] login(HttpServletRequest request, HttpServletResponse response) throws AutoLoginException { Object parameters = request.getAttribute("javax.servlet.forward.query_string"); Map<String, String> x = parserClass.parsing(parameters.toString()); System.out.println("voornaam: " + geparsdeParameters.get("tokenvalue1")); try { return null; } catch (Exception e) { throw new AutoLoginException(e); } } Since the hook doesn't start when I add the filtering I removed it and just tried: http://localhost:8080/c/portal/login?tokenvalue1=55 but when I check my tomcat I see: Error XYZ Url: url myUsedUrl exception null Also I tried adding some util classes but I got: classnotfoundexceptions. Is there anything specific I have to do when I add extra classes in a hook? Any advice/input would be appreciated. Or someone's ear I could lend so I could mail them a little bit so I could pick their brain a bit would be really appreciated since I don't know anyone who programs for liferay.

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• javafx doesnt repaint label till method has finished, why?

  - by jeff porter

  Hi all, I have a JavaFX app with a some code like this... public class MainListener extends EventListener{ override public function event (arg0 : String) : Void { statusText.content = arg0; } } statusText is defined like this... var statusText = Text { x: 30 y: stageHeight - 40 font: Font { name: "Bitstream Vera Sans Bold" size: 10 } wrappingWidth: 420 fill: Color.WHITE textAlignment: TextAlignment.CENTER content: "Status: awaiting DBF file." }; I also have some other Javacode that is load data, much like this.. public ArrayList<CustomerRecord> read(EventListener listener) { ArrayList<CustomerRecord> listOfCustomerRecords = new ArrayList<CustomerRecord>(); listener.event("Status: Starting read"); // ** takes a while... List<Map<String, CustomerField>> customerRecords = new Reader(file).readData(listener); // ** long running method over. listener.event("Status: Loaded all customers, count:" + listOfCustomerRecords.size()); return listOfCustomerRecords; } Now while the last method is in its long running call, I would expect to see my statusText updated to have 'Status: Starting read', but its doesn't. Its only when the read() method returns that the text is updated. If its was 'straight' java I would presume that the long running job is hogging the CPU, or the statusText needed to have repaint() called on it. Can anyone give me any ideas? Thanks Jeff Porter

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• Consistent Equals() results, but inconsistent TreeMap.containsKey() result

  - by smessing

  I have the following object Node: private class Node implements Comparable<Node>(){ private String guid(); ... public boolean equals(Node o){ return (this == o); } public int hashCode(){ return guid.hashCode(); } ... } And I use it in the following TreeMap: TreeMap<Node, TreeSet<Edge>> nodes = new TreeMap<Node, TreeSet<Edge>>(); Now, the tree map is used in a class called Graph to store nodes currently in the graph, along with a set of their edges (from the class Edge). My problem is when I try to execute: public containsNode(n){ for (Node x : nodes.keySet()) { System.out.println("HASH CODE: "); System.out.print(x.hashCode() == n.hashCode()); System.out.println("EQUALS: "); System.out.print(x.equals(n)); System.out.println("CONTAINS: "); System.out.print(nodes.containsKey(n)); System.out.println("N: " + n); System.out.println("X: " + x); } } I sometimes get the following: HASHCODE: true EQUALS: true CONTAINS: false N: foo X: foo Anyone have an idea as to what I'm doing wrong? I'm still new to all this, so I apologize in advance if I'm overlooking something simple (I know hashCode() doesn't really matter for TreeMap, but I figured I'd include it).

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• how to read http response soap headers from web service response in proxy class

  - by Fabricio

  I'm having some problems with one webservice that i'm working with. I generated a proxy class with wsdl.exe that comes with .net framework. But that webservice return a header that isnt not mapped by the wsdl. I must map the header sop because it contains some properties that i have to read and work with. how can i read the soap's header collection? Ex.: <soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"> <soap:Header xmlns="http://xml.amadeus.com/ws/2009/01/WBS_Session-2.0.xsd"> <Session> <SessionId>545784545</SessionId> <SequenceNumber>1</SequenceNumber> <SecurityToken>asd7a87sda89sd45as4d5a4</SecurityToken> </Session> </soap:Header> <soap:Body> <TAM_Altea_Seguranca_AutenticarRS xmlns="http://xml.amadeus.com/2009/04/TAM/TAM_Altea_Seguranca_AutenticarRS_2.0"> <statusDoProcesso> <codigoDoStatus>P</codigoDoStatus> </statusDoProcesso> </TAM_Altea_Seguranca_AutenticarRS> </soap:Body> </soap:Envelope> I need to read the SOAP:HEADER - Session.

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• Test multiple domains using ASP.NET development server

  - by Pete Lunenfeld

  I am developing a single web application that will dynamically change its content depending on which domain name is used to reach the site. Multiple domains will point to the same application. I wish to use the following code (or something close) to detect the domain name and perform the customizations: string theDomainName = Request.Url.Host; switch (theDomainName) { case "www.clientone.com": // do stuff break; case "www.clienttwo.com": // do other stuff break; } I would like to test the functionality of the above using the ASP.NET development server. I created mappings in the local HOSTS file to map www.clientone.com to 127.0.0.1, and www.clienttwo.com to 127.0.0.1. I then browse to the application with the browser using www.clinetone.com (etc). When I try to test this code using the ASP.net development server the URL always says localhost. It does NOT capture the host entered in the browser, only localhost. Is there a way to test the URL detection functionality using the development server? Thanks.

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• Performance issue on Android's MapView Navigation-App

  - by poeschlorn

  Hey Guys, I've got a question on making an navigation app more faster and more stable. The basic layer of my app is a simple mapview, covered with several overlays (2 markers for start and destination and one for the route). My idea is to implement a thread to display the route, so that the app won't hang up during the calculation of a more complex route (like it does right now). After implementing the thread there are no updates shows any more, maybe you can help me with a short glance at an excerpt of my code below: private class MyLocationListener implements LocationListener { @Override public void onLocationChanged(Location loc) { posUser = new GeoPoint((int) (loc.getLatitude() * 1E6), (int) (loc .getLongitude() * 1E6)); new Thread(){ public void run(){ mapView.invalidate(); // Erase old overlays mapView.getOverlays().clear(); // Draw updated overlay elements and adjust basic map settings updateText(); if(firstRefresh){ adjustMap(); firstRefresh = false; } getAndPaintRoute(); drawMarkers(); } }; } Some features have been summarized to a method like "drawMarkers()" or "updateText()"...(they don't need any more attention ;-))

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• How do I find the module dependencies of my Perl script?

  - by zoul

  I want another developer to run a Perl script I have written. The script uses many CPAN modules that have to be installed before the script can be run. Is it possible to make the script (or the perl binary) to dump a list of all the missing modules? Perl prints out the missing modules’ names when I attempt to run the script, but this is verbose and does not list all the missing modules at once. I’d like to do something like: $ cpan -i `said-script --list-deps` Or even: $ list-deps said-script > required-modules # on my machine $ cpan -i `cat required-modules` # on his machine Is there a simple way to do it? This is not a show stopper, but I would like to make the other developer’s life easier. (The required modules are sprinkled across several files, so that it’s not easy for me to make the list by hand without missing anything. I know about PAR, but it seems a bit too complicated for what I want.) Update: Thanks, Manni, that will do. I did not know about %INC, I only knew about @INC. I settled with something like this: print join("\n", map { s|/|::|g; s|\.pm$||; $_ } keys %INC); Which prints out: Moose::Meta::TypeConstraint::Registry Moose::Meta::Role::Application::ToClass Class::C3 List::Util Imager::Color … Looks like this will work.

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• Does Security Trimming work with Web Forms Routing?

  - by Slauma

  In my web.config I have configured a SiteMapProvider with securityTrimmingEnabled="true" and on my main master page is an asp:Menu control bound to an asp:SiteMapDataSource. In addition I have configured restricted access to all pages in a subfolder "Admin" (using another web.config in this subfolder). If I put a sitemapNode in Web.sitemap... <siteMapNode url="~/Admin/Default.aspx" title="Administration" description="" > ... only users in role "Admin" will have the menu item related to that siteMapNode. So this is working fine and as intended. Now I have defined a URL route in Global.asax to map the physical file to a new URL: System.Web.Routing.RouteTable.Routes.MapPageRoute("AdminHomeRoute", "Administration/Home", "~/Admin/Default.aspx"); But when I use this route-URL in the SiteMap file... <siteMapNode url="Administration/Home" title="Administration" description="" > ... it seems that security trimming does not work: The menu item is visible for all users. (Access to the page is still restricted though, so selecting the menu item by non-Admin users does not navigate to the restricted page.) Question: Is there any setting I've missed so far to make security trimming working with URL routing in ASP.NET 4.0 Web Forms? Did I do something wrong? Is there any work-around? Thank you for help!

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• rotate an image aroound a point

  - by Girish

  Hi all, I have an image which is of rectangular dimension, eg 30 x 60 pixels I want to rotate this image around the bottom center of the image, i.e i want to set the pivot in the above example as (15, 60 )pixel. I am using a drawble and matrix to get this done, whatever i try i always end up rotating around center of the image. Code is : Bitmap bitmapOrg = BitmapFactory.decodeFile("/sdcard/DCIM/2010-06-01_15-32-42_821.jpg"); // float angle = (angle + 10.0f)%360.0f; if(null !=bitmapOrg) { int width = bitmapOrg.getWidth(); int height = bitmapOrg.getHeight(); int newWidth = 15; int newHeight = 15; // calculate the scale - in this case = 0.4f float scaleWidth = ((float) newWidth) / width; float scaleHeight = ((float) newHeight) / height; /* Canvas c = new Canvas(bitmapOrg); float px = ; float py; c.rotate(angle, px, py)*/ // createa matrix for the manipulation Matrix matrix = new Matrix(); // resize the bit map matrix.postScale(scaleWidth, scaleHeight); // rotate the Bitmap // matrix.postRotate(45); // recreate the new Bitmap Bitmap resizedBitmap = Bitmap.createBitmap(bitmapOrg, 0, 0, width, height, matrix, true); // make a Drawable from Bitmap to allow to set the BitMap // to the ImageView, ImageButton or what ever BitmapDrawable bmd = new BitmapDrawable(resizedBitmap); ImageView imageView = new ImageView(this); // set the Drawable on the ImageView imageView.setImageDrawable(bmd); // center the Image imageView.setScaleType(ScaleType.CENTER); // imageView.layout(100, 300, 0, 0); // linLayout.addView(imageView); // add ImageView to the Layout linLayout.addView(imageView, new AbsoluteLayout.LayoutParams( LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT, 10, 30 ) ); can anyone let me know how to get this rectified?

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• Unidentifiable Vim Keymap

  - by asdf.qwer

  Hi I'm trying to get rid of a pesky keymapping in vim, namely \c The mapping is only loaded for latex files, so it should be related to the latex-suite. It's annoying, because it can't type \cite without this keymap ruining everything. I can unmap it "manually" by typing: :unmap! \c But this doesn't work when I put that into my ~/.vimrc file because it says there's no such keymap. I think this is because the keymap is loaded after .vimrc, although I'm not sure. I've tried locate in bash to locate all files on my system that start have "vim" in their filename, and subsequently grep keyword $filename to find all references to keyword that should be relevant. The keyword I search for is "Traditional" because that's what the mapping is called (that's what I find by typing :map! in vim normal mode). It finds some entries that contain "Traditional" but nothing that corresponds to \c, except in the file: ~/.gnome2/gvim-sA9LOO-session.vim But this file is not used by vim when starting up, as far as I know. Anyone know any fix?

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• Hibernate ManyToMany and superclass mapping problem

  - by Jesus Benito

  Hi all, I need to create a relation in Hibernate, linking three tables: Survey, User and Group. The Survey can be visible to a User or to a Group, and a Group is form of several Users. My idea was to create a superclass for User and Group, and create a ManyToMany relationship between that superclass and Survey. My problem is that Group, is not map to a table, but to a view, so I can't split the fields of Group among several tables -which would happen if I created a common superclass-. I thought about creating a common interface, but mapping to them is not allowed. I will probably end up going for a two relations solution (Survey-User and Survey-Group), but I don't like too much that approach. I thought as well about creating a table that would look like: Survey Id | ElementId | Type ElementId would be the Group or UserId, and the type... the type of it. Does anyone know how to achieve it using hibernate annotations? Any other ideas? Thanks a lot

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• MVVM pattern: ViewModel updates after Model server roundtrip

  - by Pavel Savara

  I have stateless services and anemic domain objects on server side. Model between server and client is POCO DTO. The client should become MVVM. The model could be graph of about 100 instances of 20 different classes. The client editor contains diverse tab-pages all of them live-connected to model/viewmodel. My problem is how to propagate changes after server round-trip nice way. It's quite easy to propagate changes from ViewModel to DTO. For way back it would be possible to throw away old DTO and replace it whole with new one, but it will cause lot of redrawing for lists/DataTemplates. I could gather the server side changes and transmit them to client side. But the names of fields changed would be domain/DTO specific, not ViewModel specific. And the mapping seems nontrivial to me. If I should do it imperative way after round-trip, it would break SOC/modularity of viewModels. I'm thinking about some kind of mapping rule engine, something like automappper or emit mapper. But it solves just very plain use-cases. I don't see how it would map/propagate/convert adding items to list or removal. How to identify instances in collections so it could merge values to existing instances. As well it should propagate validation/error info. Maybe I should implement INotifyPropertyChanged on DTO and try to replay server side events on it ? And then bind ViewModel to it ? Would binding solve the problems with collection merges nice way ? Is EventAgregator from PRISM useful for that ? Is there any event record-replay component ? Is there better client side pattern for architecture with server side logic ?

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• Examples of monoids/semigroups in programming

  - by jkff

  It is well-known that monoids are stunningly ubiquitous in programing. They are so ubiquitous and so useful that I, as a 'hobby project', am working on a system that is completely based on their properties (distributed data aggregation). To make the system useful I need useful monoids :) I already know of these: Numeric or matrix sum Numeric or matrix product Minimum or maximum under a total order with a top or bottom element (more generally, join or meet in a bounded lattice, or even more generally, product or coproduct in a category) Set union Map union where conflicting values are joined using a monoid Intersection of subsets of a finite set (or just set intersection if we speak about semigroups) Intersection of maps with a bounded key domain (same here) Merge of sorted sequences, perhaps with joining key-equal values in a different monoid/semigroup Bounded merge of sorted lists (same as above, but we take the top N of the result) Cartesian product of two monoids or semigroups List concatenation Endomorphism composition. Now, let us define a quasi-property of an operation as a property that holds up to an equivalence relation. For example, list concatenation is quasi-commutative if we consider lists of equal length or with identical contents up to permutation to be equivalent. Here are some quasi-monoids and quasi-commutative monoids and semigroups: Any (a+b = a or b, if we consider all elements of the carrier set to be equivalent) Any satisfying predicate (a+b = the one of a and b that is non-null and satisfies some predicate P, if none does then null; if we consider all elements satisfying P equivalent) Bounded mixture of random samples (xs+ys = a random sample of size N from the concatenation of xs and ys; if we consider any two samples with the same distribution as the whole dataset to be equivalent) Bounded mixture of weighted random samples Which others do exist?

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• How to customize RESTful Routes in Rails (basics)

  - by viatropos

  I have read through the Rails docs for Routing, Restful Resources, and the UrlHelper, and still don't understand best practices for creating complex/nested routes. The example I'm working on now is for events, which has_many rsvps. So a user's looking through a list of events, and clicks register, and goes through a registration process, etc. I want the urls to look like this: /events /events/123 # possible without title, like SO /events/123/my-event-title # canonical version /events/my-category/123/my-event-title # also possible like this /events/123/my-event-title/registration/new ... and all the restful nested resouces. Question is, how do I accomplish this with the minimal amount of code? Here's what I currently have: map.resources :events do |event| event.resources :rsvps, :as => "registration" end That gets me this: /events/123/registration What's the best way to accomplish the other 2 routes? /events/123/my-event-title # canonical version /events/my-category/123/my-event-title # also possible like this Where my-category is just an array of 10 possible types the event can be. I've modified Event#to_param to return "#{self.id.to_s}-#{self.title.parameterize}", but I'd prefer to have /id/title with the whole canonical-ness

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• Swing: what to do when a JTree update takes too long and freezes other GUI elements?

  - by java.is.for.desktop

  Hello, everyone! I know that GUI code in Java Swing must be put inside SwingUtilities.invokeAndWait or SwingUtilities.invokeLater. This way threading works fine. Sadly, in my situation, the GUI update it that thing which takes much longer than background thread(s). More specific: I update a JTree with about just 400 entries, nesting depth is maximum 4, so should be nothing scary, right? But it takes sometimes one second! I need to ensure that the user is able to type in a JTextPane without delays. Well, guess what, the slow JTree updates do cause delays for JTextPane during input. It refreshes only as soon as the tree gets updated. I am using Netbeans and know empirically that a Java app can update lots of information without freezing the rest of the UI. How can it be done? NOTE 1: All those DefaultMutableTreeNodes are prepared outside the invokeAndWait. NOTE 2: When I replace invokeAndWait with invokeLater the tree doesn't get updated. NOTE 3: Fond out that recursive tree expansion takes far the most time. NOTE 4: I'm using custom tree cell renderer, will try without and report. NOTE 4a: My tree cell renderer uses a map to cache and reuse created JTextComponents, depending on tree node (as a key). CLUE 1: Wow! Without setting custom cell renderer it's 10 times faster. I think, I'll need few good tutorials on writing custom tree cell renderers.

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• Does isEmpty method in Stream evaluate the whole Stream?

  - by abhin4v

  In Scala, does calling isEmtpy method on an instance of Stream class cause the stream to be evaluated completely? My code is like this: import Stream.cons private val odds: Stream[Int] = cons(3, odds.map(_ + 2)) private val primes: Stream[Int] = cons(2, odds filter isPrime) private def isPrime(n: Int): Boolean = n match { case 1 => false case 2 => true case 3 => true case 5 => true case 7 => true case x if n % 3 == 0 => false case x if n % 5 == 0 => false case x if n % 7 == 0 => false case x if (x + 1) % 6 == 0 || (x - 1) % 6 == 0 => true case x => primeDivisors(x) isEmpty } import Math.{sqrt, ceil} private def primeDivisors(n: Int) = primes takeWhile { _ <= ceil(sqrt(n))} filter {n % _ == 0 } So, does the call to isEmpty on the line case x => primeDivisors(x) isEmpty cause all the prime divisors to be evaluated or only the first one?

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• Translating Where() to sql

  - by MBoros

  Hi. I saw DamienG's article (http://damieng.com/blog/2009/06/24/client-side-properties-and-any-remote-linq-provider) in how to map client properties to sql. i ran throgh this article, and i saw great potential in it. Definitely mapping client properties to SQL is an awesome idea. But i wanted to use this for something a bit more complicated then just concatenating strings. Atm we are trying to introduce multilinguality to our Business objects, and i hoped we could leave all the existing linq2sql queries intact, and just change the code of the multilingual properties, so they would actually return the given property in the CurrentUICulture. The first idea was to change these fields to XMLs, and then try the Object.Property.Elements().Where(...), but it got stuck on the Elements(), as it couldnt translate it to sql. I read somewhere that XML fields are actually regarded as strings, and only on the app server they become XElements, so this way the filtering would be on the app server anyways, not the DB. Fair point, it wont work like this. Lets try something else... SO the second idea was to create a PolyGlots table (name taken from http://weblogic.sys-con.com/node/102698?page=0,1), a PolyGlotTranslations table and a Culture table, where the PolyGlots would be referenced from each internationalized property. This way i wanted to say for example: private static readonly CompiledExpression<Announcement, string> nameExpression = DefaultTranslationOf<Announcement> .Property(e => e.Name) .Is(e=> e.NamePolyGlot.PolyGlotTranslations .Where(t=> t.Culture.Code == Thread.CurrentThread.CurrentUICulture.Name) .Single().Value ); now unfortunately here i get an error that the Where() function cannot be translated to sql, what is a bit disappointing, as i was sure it will go through. I guess it is failing, cause the IEntitySet is basically an IEnumerable, not IQueryable, am i right? Is there another way to use the compiledExpressions class to achieve this goal? Any help appreciated.

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